Zinc aluminum alloy

ABSTRACT

A zinc-aluminum alloy comprises 18-24 % aluminum, 0.0005 - 0.05 % magnesium, 0.0025 - 0.25 % nickel, balance high-grade zinc. The form stability of the alloy can be improved by homogenizing it at a temperature above 275* to 380* C and aging it at a temperature above 80* C up to below 275* C for a time of 0.2 to 5 hours. The alloy has a high ductility, together with a high creep resistance.

United States Patent 1 Peizel 1 Aug. 28, 1973 [54] ZINC'ALUMINUM ALLOY FOREIGN PATENTS R APPLICATIONS 1 1 lnvemofl Erich Pellet Puchheim, Germany 759,258 8/1952 Germany 75/178 AM Assigneez stolbergehzink AG Fur Bergbau 335,270 2/1936 Italy 75/178 AM Und Huttenbetrieb, Aachen, 7 Germany Primary Examiner-L. Dewayne Rutledge Assistant Examiner-E. L. Weise [22] F'led: 1971 AtrorneyMihae1 S. Striker [21] App]. No.: 120,718

[57] ABSTRACT [30] Foreign Application Priority Data A zinc-aluminum alloy comprises 18-24 aluminum,

' Mar. 5. I970 Germany P 10 299.2 0.0005 0.05 magnesium. 0.0025 n k l.

balance high-grade zinc. [52] US. Cl. 78/178 A, 148/127 The f Stability f the alloy can be improved by [51 hit. Cl. C22C 17/00 homogenizing i at a temperature above 275 to 3 0 C [58] Field of Search /178 A, 178 AM and aging it at a temperature above C up to below 275 C for a time of 0.2 to 5 hours. [56] References Cited The alloy has a high ductility, together with a high UNITED STATES PATENTS Creep resistance 1,663,215 3/1928 Peirce et a1. 75/178 AM 2 00 529 7 1935 6 Claims, N0 Drawlngs Werley 75/178 A ZINC-ALUMINUM ALLOY BACKGROUND OF THE INVENTION The invention relates to a zinc-aluminum alloy.

Sheets and strips made of wrought zinc alloys, in addition to high strength, must normally have good shaping properties, both with regard to working by folding and bending and working by stamping and drawing.

Excellent wrought alloys with a high ductility are formed by binary zinc-aluminum alloys with about 1-63% aluminum and 3799% zinc. The mixed crystalls of these alloys are caused to break down to a super-fine grain eutectic structure by suitable heat treatment. In this manner an alloy is formed of high ductility which possesses the property to undergo strong plastic deformation at extremely low mechanical stresses (DDRP [East German Patent] 4822; Sauerwald, F.: Arch. Metallkde, H. 5, 1949, p. 165; Mitbauer, H. and F. Sauerwald: Z. Metallkde, 43, 1952, p. 244; Schultze W. and F. Sauerwald: Z. Metallkde, 53, 1962, p. 660).

These alloys usually reach tensile strength values between 16 and 20 kp/mm and elongation values of above 100%. Strips and sheets made from these alloys are therefore free of breaks when folded by 180 and are well suited for deep-drawing and for working in a vacuum shaping process. The creep resistance of these alloys, however, at an elongation of 1 percent per year is 0.4 kp/mm which is entirely inadequate for practical purposes.

The creep resistance of the zinc-aluminum alloy s can be improved by small additions of nickel which have a degree of solubility in solid aluminum and zinc.

(Wolf, W.: Zink ABC, Berlin 1950, p. 119; Burkhardt, A.: Technologie der Zinklegierungen, Berlin, 1940, pp. 22-24).

In other respects, however, the nickel causes the alloy to become more brittle. The excellent ductility of these alloys thus is almost completely lost and the elongation value at a tensile stress of 40 kp/mm is reduced to below percent.

According to a different proposal which is not prior art, there is added to an 1824% aluminum-containing alloy nickel within the range of 0.1 to 1.5% and the alloy is subjected to homogenizing for an extended period of time at temperatures between 300 and 380C. By a subsequent cooling to temperatures below 275 C This formation of a coarse grain structure can be obviated by adding to the nickel-containing zincaluminum alloy more than 0.05 and up to 0.25% magnesium and heating the alloy to a temperature in the range between 280 and 380 C, followed by subsequent cooling at a specific cooling rate (German published application 1 922 213). These steps retain the fine crystal structure which is necessary for a high ductility.

It has, however, been found that if for instance strips which are machine-rolled from this type of zincaluminum alloy, for instance to form channel-shaped structures or tubular structures, the rolled strip, when leaving the machine, will only partly retain the imposed deformation because of the strong tendency to a rebound caused by the high elasticity of the alloy.

It is therefore an object of the invention to provide for a zinc-aluminum alloy which avoids the described shortcomings.

SUMMARY or THE INVENTION The invention resides in a zinc-aluminum alloy which comprises 18 24 aluminum, 0.0005 0.05 magnesium, 0.0025 0.25 nickel, balance high-grade zinc.

DETAILED DESCRIPTION OF THE INVENTION AND OF SPECIFIC EMBODIMENTS Preferably, the aluminum content of the alloy of the invention is 21 The preferred magnesium contentis 0.001 to 0.01 magnesium. The nickel content is at least five time the specific amount of magnesium present.

The preferred aging temperature is between 120 and 200 C.

The described process features, in combination with the composition of the alloy, result in a Ni Mg phase which is essentially the reason for the increased ductility, together with a simultaneous increase of the creep resistance.

The following examples will further describe and i1- lustrate the invention, and furnish comparisons with prior-artalloys and alloys otherwise outside the scope a break down of the formed mixed crystals is obtained I to form a fine grain eutectic structure. This results in a substantial improvement of the ductility.

The break down of the mixed crystals can be substantially retarded by adding magnesium to the zincaluminum alloy in order to suppress the intercrystalline corrosion. The reason is that the solubility of the magnesium in solid zinc is reduced. The increase of strength is therefore accompanied again by a decrease of the ductility. The effect of the magnesium to make the alloy more brittle can be avoided only by keeping the magnesium content of the alloy at a level below 0.0005%. When a higher content of magnesium is used, it is necessary to cause the fine crystalline break down of the mixed crystals by an additional heat treatment at temperatures up to 275. This type of heat treatment leads to the formation of a coarse grain which in turn results again in a decrease of the ductility (Mitbauer, H. and F. Sauerwald: Z. Metallkde., 43, 1952, p. 244-249).

of the invention.

The alloys described in the invention, in each case, were made by melting the components at a temperature of 450C and casting the alloy to ingots of the thickness of 4 cm. After a subsequent homogenizing treatment, at a temperature of 350C, each ingot was hot rolled at a temperature of 300C in several passes to a final sheet thickness of 1 mm.

EXAMPLE 1 A prior-art alloy, consisting of 21% aluminum 79% zinc and formed into a sheet as described before had the following mechanical properties:

tensile strength 20 kplmrn' elongation creep resistance 0.4 kp/mm EXAMPLE 2 A sheet was formed from a prior-art alloy comprising 21 aluminum 0.2 nickel balance high-grade zinc The sheet had the following properties tensile strength 21 kp/mm elongation 130% creep resistance 12 kp/mm EXAMPLE 3 A sheet was formed of a prior-art alloy comprising 21% aluminum 0.04% magnesium balance high-grade zinc The sheet had the following properties:

tensile strength 30 kp/mm elongation creep resistance 6.5 kp/mm After heat-aging for 2 hours, at 180C, the mechanical properties were improved as follows:

tensile strength 33 kp/mm elongation creep resistance 7.0 kp/mm EXAMPLE 4 tensile strength 30 kp/mm elongation 15 creep resistance 6.5 kp/mm After heat-aging at a temperature of 180 C for 2 5 hours, the mechanical properties were improved to the following figures:

tensile strength 33 kp/mm elongation 80 creep resistance 8.0 kp/mm.

EXAMPLE 5 In this example a sheet was formed as described from an alloy according to the present invention which comprised:

18 aluminum 0.1% nickel 0.001% magnesium balance high-grade zinc The following values were found:

tensile strength 29 kp/mm elongation l5 creep resistance 6 kp/mm After heat-aging at a temperature of 180 C for two hours, the mechanical properties were improved to the following figures:

tensile strength 32 kp/mm elongation 110 creep resistance 7.5 kp/mm EXAMPLE 6 In this example a sheet was formed as described from an alloy according to the present invention which comprised:

24 aluminum 0.25 nickel 0.01 magnesium balance high-grade zinc The following values were found:

tensile strength -30 kp/mm elongation l5 creep resistance 6.5 kp/mm After heat-aging at a temperature of 180 C for 2 hours, the mechanical properties were improved to the following figures:

tensile strength 31 kp/mm elongation creep resistance 7.5 kp/mm EXAMPLE 7 In this example a sheet was formed as described from an alloy according to the present invention which comprised:

21 aluminum 0.025 nickel 0.005 magnesium balance high-grade zinc The following values were found:

tensile strength 27 kp/mm elongation 15 1 creep resistance 5 kp/mm After heat aging at a temperature of 180 C for 2 hours, the mechanical properties were improved to the following figures:

tensile strength 29 kp/mm elongation creep resistance 7.0 kp/mm EXAMPLE 8 In this example a sheet was formed as described from an alloy according to the present invention which comprised:

21 aluminum 0.0025 nickel 0.0005 magnesium balance high-grade zinc The following values were found:

tensile strength 26 kp/mm elongation l5 creep resistance 4,5 kp/mm After heat aging at a temperature of C for 2 hours,

the mechanical properties were improved-to the following figures:

tensile strength 28 kp/mm elongation 75 creep resistance 5.5 kp/mm Comparing the tensile strength, the elongation and the creep resistance, particularly as between the sheets of Example 3 and Examples 4, 5, 6, 7 and 8, it will be noted that the elongation of the zinc-aluminum alloy of the invention is improved by more than five times by means of the heat treatment of the invention, together with a simultaneous increase of the creep resistance. The ductility thus obtained, although it is not quite as good as that of the zinc-aluminum alloys of Examples 1 and 2, is entirely adequate for meeting the shaping properties of industrial practice.

Without further analysis, the foregoing will so fully reveal the gist of the invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

4. The alloy of claim 1, wherein aluminum is present in an amount of 21 and the magnesium content is 0.001 to 0.01 and the nickel content is 0.005 to 0.05

5. The alloy of claim 1, which comprises 2] aluminum, 0.2 nickel, 0.04 magnesium, balance zinc.

6. The alloy of claim 1, wherein the amount of nickel present is substantially equal to at least five times the specific amount of magnesium present.

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2. The alloy of claim 1, in which aluminum is present in an amount of about 21 percent.
 3. The alloy of claim 1, in which the magnesium content is 0.001 to 0.01 % and the nickel content is 0.005 to 0.05 percent.
 4. The alloy of claim 1, wherein aluminum is present in an amount of 21 % and the magnesium content is 0.001 to 0.01 % and the nickel content is 0.005 to 0.05 %.
 5. The alloy of claim 1, which comprises 21 % aluminum, 0.2 % nickel, 0.04 % magnesium, balance zinc.
 6. The alloy of claim 1, wherein the amount of nickel present is substantially equal to at least five times the specific amount of magnesium present. 